Police said a school resource officer requested help at about 10:38 a.m. Wednesday for two physical altercations that broke out during a passing period at the school.
One student was transported to a hospital with a head injury, police said.
Yorkville police and Yorkville CUSD 115 are investigating the incident and charges could be announced later Thursday.
"We take the safety and health of our students and staff very seriously and I would like to thank the Yorkville Police Department for their quick response and attention to the safety of our students," Yorkville HS principal David Travis said in a letter to parents.